For correct diagnosis of various cancer diseases biopsies are taken via a lumen of an endoscope or via needle or via catheter. In order to find the correct position to take the biopsy, various imaging modalities are used such as X-ray, CT, Magnet Resonance Imaging (MRI) and ultrasound. Although helpful, these methods of guidance are far from optimal.
Interventional procedures such as biopsy taking with needles are carried out more and more under MRI guidance. This puts strong demands on the needle material. Needles are requested, which are compatible with high magnetic fields such as 3 T. Here conventional material applied for MR compatible systems such as Ti and Ti alloys are coming to their limits. With increasing magnetic fields up to 3 T, these needles can show during the procedure local heat caused by eddy currents and are therefore not suited.
To realize high magnetic field compatible needles, today new technologies for needles are studied. This comprises needles based on pure organic material e.g. plastic as well as plastic needles with ceramic tips.
The plastic needles are much more flexible than the metal needles and make needle positioning difficult. Furthermore plastic needles do not have very sharp tips, which is for interventional procedures not the optimum.
Further problems directly related to biopsy are the resolution of the imaging system which is limited and, furthermore, these imaging modalities cannot in most cases discriminate normal and neoplastic tissue and further differentiate between benign and malignant tissue.
As a result of that, there is a high level of uncertainty whether an appropriate tissue specimen is taken.
In addition to that, the biopsies are often taken blindly, with limited feedback of where the needle is relative to the target tumor, which leads to an additional uncertainty whether the lesion has been hit by the needle. It is clear that guidance improvement is required to target the biopsy needle to the correct position in the tissue.
A further limitation is that even if one could guide the biopsy needle to the exact location corresponding to the pre-recorded image, one is never sure that this is the exact location due to the compressibility of the tissue. Due to the force of the biopsy needle on the tissue during advancement, the tissue may become deformed.
If the specimen taken appears to be cancerous, in most cases this cancerous tissue will be removed by surgery (especially when the tumor is well localized) or treated percutaneously using RF, microwave, or cryoablation.
The surgical approach is confounded by the fact that the surgeons typically use only their eyes and hands (palpation) to find the tumor and have to rely on the information of pre-recorded images. These pre-recorded images provide information on the position of the tumor but do not always clearly show the tumor boundaries. Sometimes, the surgeon implants a marker under image guidance, providing him or her with a reference point to focus on during the surgical procedure. Again guiding the localization wire to the correct position is difficult.
The biopsy device may also be used as a device for administering drugs or a therapy (like ablation) at a certain position in the body without removing tissue, for instance for injecting a fluid at the correct location of the affected body part. The same drawbacks apply for these interventions where it is difficult to guide the biopsy device to the correct location.